Antioxidant Research and Its Application to Feeding Horses

April 26, 2010

Carey Williams, Ph.D., an associate equine specialist at
Rutgers, the State University of New Jersey, described the importance of
antioxidants in equine nutrition, highlighting the studies she has undertaken
during her tenure as a researcher.

Oxidative stress occurs in horses at all times but is
accelerated during exercise, aging, and disease processes. Defense mechanisms
against oxidative stress include vitamins E, C, and A as well as certain
enzymes. Though oxidative stress cannot be directly measured with ease,
intermediate or end products during oxidation can be measured.

The first two studies discussed by Williams involved 80-km
endurance rides. In the first study, 46 horses were separated into two groups
and given either vitamin E, or vitamin E and vitamin C. for three weeks prior
to the race Thirty-four horses completed the race. Conclusions derived include
that horses were in fact undergoing oxidative stress, though the effects of antioxidant
supplementation could not be evaluated as beneficial because there was no
control group used in the study.

In the second study, 40 horses were used. Two groups were
created following the race: finishers and nonfinishers. Levels of vitamin E consumed
prior to the races differed considerably, ranging from 1150 to 4700 IU/day.
Most horses with high vitamin E intakes had greater access to pasture than
horses with lower intakes. A negative correlation was found between the vitamin
E intake and muscle damage, and a positive correlation was found with intake
and plasma vitamin E. A negative correlation was found between finishing time
and vitamin E intake for the 24 horses that finished the race. According to
Williams, one hypothesis for this finding could be that the higher-placed
horses were working at greater intensity and/or being trained harder, thus
having more sweet feed or supplements in the diet. Their higher level of conditioning
may also have allowed these horses to work harder with lower muscle enzyme
activities.

In the third study, treadmill-trained Arabians were
separated into three groups: vitamin E, lopoic acid, and control. A simulated
endurance exercise test of three exercise bouts totaling 55 km, with 20-minute
vet checks separating each. Apoptosis (programmed cell death) was measured.
Results showed that apoptosis occurs in white blood cells during exercise, and
it can be moderated by supplementation with vitamin E or lopoic acid. The
vitamin E group had 50% lower and the lopoic acid group had 40% lower apoptosis
compared to the control group. The increase in antioxidant status in the
vitamin E and lipoic acid groups aided the white blood cells in scavenging the
free radicals, thereby triggering the apoptosis in these cells.

The studies presented by Williams have positively shown
oxidative stress during endurance, intense, and treadmill exercise, though
oxidative stress and muscle-enzyme leakage was dependent on numerous factors
(environmental conditions, level of exercise, conditioning of horse, for
example). Supplementing with antioxidants decreases oxidative stress and
muscle-enzyme leakage.